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Term Paper
Analysis and Design of
Infor
mation Systems
Topic: Different design techniques
Rishab Mehta Reg. No.
3450070062Roll No.59 Section: c1802
Declaration:
I declare that this assignment is my individual work. I have not
copied from any other students work or from any other source
except where due acknowledgment is made explicitly in thetext, nor has any part been written for me by another person.
Students Signature:
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Rishab Mehta
Index
1. Introduction 3
a. What is a system?
b. SDLC
2. System Design..........................................................................................................4
a. Preliminary or general design
b. Structure or detailed design
i. Flowchart -4
ii. Data flow diagram (DFDs) -5
iii. Data dictionary -6
iv. Structured English -6
v. Decision table -6
vi. Decision tree -7
3. Techniques7
4. Bibliography.8
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1. Introduction:
Before discussing the different design techniques used in system designing we are going to
discuss some basic terms used and there meaning.
a. What is a System?
A collection of components that work together to realize some objective forms a system.Basically there are three major components in every system, namely input, processing and
output.
b. Briefing System Development Life Cycle (SDLC)
The Software Development Lifecycle (SDLC) is a conceptual model used in projectmanagement that describes the stages involved in an information system development
project, from an initial feasibility study through maintenance of the completed application.
The figure below shows the different phases followed in SDLC:
Here the design phase can be divided into two parts:
System design
Coding
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2. System Design
Based on the user requirements and the detailed analysis of a new system, the new system
must be designed. This is the phase of system designing. It is a most crucial phase in the
development of a system. Normally, the design proceeds in two stages:
c. Preliminary or general design
d. Structure or detailed design
a. Preliminary or general design: In the preliminary or general design, the features of the
new system are specified. The costs of implementing these features and the benefits to bederived are estimated. If the project is still considered to be feasible, we move to the
detailed design stage.
b. Structure or Detailed design: In the detailed design stage, computer oriented work
begins in earnest. At this stage, the design of the system becomes more structured. Structuredesign is a blue print of a computer system solution to a given problem having the same
components and inter-relationship among the same components as the original problem.
Input, output and processing specifications are drawn up in detail. In the design stage, theprogramming language and the platform in which the new system will run are also decided.
There are several tools and techniques used for designing. These tools and techniquesare:
i. Flowchart
ii. Data flow diagram (DFDs)
iii. Data dictionary
iv. Structured English
v. Decision table
vi. Decision tree
i. Flowcharts
Systems flowcharts are graphic illustrations of the physical flow of information through the entire
accounting system. A systems flowchart is commonly used in analysis and design. Flow-lines
represent the sequences of processes, and other symbols represent the inputs and outputs to a
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process. Accountants use system flowcharts to describe the computerized processes, manual
operations, and inputs and outputs of an application system. Auditors use system flowcharts to
identify key control points in an accounting systems internal control structure.
It is nothing but a diagrammatic representation of the various steps involved in designing a
system. Some of the boxes which are used in flowcharts are:
A flowchart consists of a set of flowchart symbols connected by arrows. Each symbol
contains information about what must be done at that point & the arrow shows the flow of
execution of the algorithm i.e. they show the order in which the instructions must be
executed. The purpose of using flowcharts is to graphically present the logical flow of data
in the system and defining major phases of processing along with the various media to be
used.
Flowcharts are of three types:
a. System flowcharts
b. Run flowcharts
c. Program flowcharts
ii. Data Flow Diagram
Data flow diagrams illustrate how data is processed by a system in terms of inputs and outputs. The
main merit of DFD is that it provides an overview of what data flows in a system, whattransformations are done on the data, what files are used and where results flow. It is a good
documentation aid which is understood by both programmers and non-programmers (i.e.,
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laypersons). As DFD specifies only what processes are performed and not how they areperformed it is easily understood by a non-programming user.
Components of DFD
DFDs are constructed using four major components:
External entries
Data stores
Processes andData flows
iii. Data Dictionary
A data dictionary is a collection of descriptions of the data objects or items in a data modelfor the benefit of programmers and others who need to refer to them. A first step in
analyzing a system of objects with which users interact is to identify each object and its
relationship to other objects. This process is called data modeling and results in a picture of
object relationships. After each data object or item is given a descriptive name, itsrelationship is described (or it becomes part of some structure that implicitly describes
relationship), the type of data (such as text or image or binary value) is described, possible
predefined values are listed, and a brief textual description is provided. This collection canbe organized for reference into a book called a data dictionary.
iv. Structured English
Structured English is a way of describing the flow of a process. The two building blocks of Structured
English are (1) structured logic or instructions organized into nested or grouped procedures,and (2) simple English statements such as add, multiply, move, etc. (strong, active, specific
verbs)
Five conventions to follow when using Structured English:
1. Express all logic in terms of sequential structures, decision structures, or iterations.
2. Use and capitalize accepted keywords such as: IF, THEN, ELSE, DO, DO WHILE,DO UNTIL, PERFORM
3. Indent blocks of statements to show their hierarchy (nesting) clearly.4. When words or phrases have been defined in the Data Dictionary, underline those
words or phrases to indicate that they have a specialized, reserved meaning.
5. Be careful when using "and" and "or" as well as "greater than" and "greater than or
equal to" and other logical comparisons.
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v. Decision Tables
The decision table is a chart with four sections listing all the logical conditions and actions.
The condition stub contains a list of all the necessary tests in a decision table. In the lower
left-hand corner of the decision table we find the action stub where one may note all theprocesses desired in a given module. Thus Action Stub contains a list of all the processes
involved in a decision table.
The upper right corner provides the space for the condition entry - all possible
permutations of yes and no responses related to the condition stub. The yes and no
possibilities are arranged as a vertical column called rules.
vi. Decision Tree
The decision tree defines the conditions as a sequence of left to right tests. A decision tree
helps to show the paths that are possible in a design following an action or decision by theuser.
Four major steps in building Decision Trees:
1. Identify the conditions2. Identify the outcomes (condition alternatives) for each decision
3. Identify the actions
4. Identify the rules.
3. Techniques:
The three most important techniques that are used in designing are:
a. Logical Data Modeling
This is the process of identifying, modeling and documenting the data requirements
of the system being designed. The data are separated into entities (things aboutwhich a business needs to record information) and relationships (the associations
between the entities).
b. Data Flow Modeling
This is the process of identifying, modeling and documenting how data moves
around an information system. Data Flow Modeling examines processes (activitiesthat transform data from one form to another), data stores (the holding areas for
data), external entities (what sends data into a system or receives data from a
system), and data flows (routes by which data can flow).
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c. Entity Behavior Modeling
This is the process of identifying, modeling and documenting the events that affecteach entity and the sequence in which these events occur.
System-Level Design Techniques addresses the development and validation of co-synthesis
techniques that allow an effective design of embedded systems. Here we have an overviewof a system-level co-design flow, illustrating through examples how system performance is
influenced at various steps of the flow including allocation, mapping, and scheduling. We
are specially emphasizing upon system-level co-synthesis techniques for architectures that
contain voltage scalable processors, which can dynamically trade-off betweencomputational performances. Throughout, the introduced co-synthesis techniques, which
target both single-mode systems and emerging multi-mode applications, are applied to
numerous benchmarks and real-life examples including a realistic smart phone.
4. Bibliography
1. http://www.wikipedia.org
2. http://www.springer.com/computer/information+systems+and+applications/
3. http://www.comp.glam.ac.uk/pages/staff/tdhutchings/chapter3.html
4. Analysis and Design of Systems - P.S. Awadh
5. Information System design and Techniques Bob McCarthy
http://www.wikipedia.org/http://www.springer.com/computer/information+systems+and+applications/http://www.comp.glam.ac.uk/pages/staff/tdhutchings/chapter3.htmlhttp://www.wikipedia.org/http://www.springer.com/computer/information+systems+and+applications/http://www.comp.glam.ac.uk/pages/staff/tdhutchings/chapter3.htmlTop Related